The present invention relates to an electrostatic actuator used for an ink jet head, a reflector type diffraction grating, a reflector type light valve, and so on, and an apparatus having such an electrostatic actuator mounted therein, and particularly relates to stabilization of driving such an electrostatic actuator.
In that which uses an electrostatic actuator, for example, in an ink jet head, precision fine machining and high accurate bonding technique are required for manufacturing the ink jet head in accordance with a demand for high definition character printing. Various kinds of manufacturing methods have been developed therefore. Of them, an ink jet head disclosed in JP-A-9-20007 has realized very high accurate bonding in a manner such that a silicon wafer having an ink cavity formed therein, and borosilicate glass having an actuator are bonded with each other by anodic bonding.
However, in the above-mentioned conventional technique, there was a problem that, after anodic bonding was completed, dielectric constant was changed by gas or the like generated inside a groove to which a driving means was attached so that electrostatic force was changed to make ink discharge unstable.
Such a problem also applied to an electrostatic actuator used for a reflector type diffraction grating, a reflector type light valve, and so on. Accordingly, there was another problem that, because of change in dielectric constant, the electrostatic force was not stabilized, and the operation of the actuator as an element was also unstable.
It is an object of the present invention to provide an electrostatic actuator and an apparatus mounted therewith, in which gas or the like generated inside a groove is absorbed by getter material so as to stabilize the electrostatic force with less time aging.
(1) In an electrostatic actuator according to the present invention comprising an insulating substrate provided with a recess portion, an electrode provided in the recess portion formed in the insulating substrate, and a thin film provided so as to cover the recess portion of the insulating substrate, wherein the thin film is transformed by electrostatic force generated by application of a voltage between the electrode and the thin film, a getter material is disposed in the recess portion or in another recess portion provided so as to communicate with the first-mentioned recess portion. Gas, moisture, and so on, in the recess portion are absorbed by this getter material. Accordingly, it is possible to prevent dielectric constant in the recess portion from changing, so that the electrostatic environment is stabilized, and the electrostatic force is therefore stabilized.
(2) In an electrostatic actuator according to the present invention as stated in the above item (1), the getter material consists of Ti or a Ti alloy. As for the Ti alloy, for example, an alloy of Ti and Zr, Ti and Al, or the like, is used.
(3) In an electrostatic actuator according to the present invention as stated in the above item (1) or (2), the getter material is heated so as to be activated after the insulating substrate and the thin film are bonded with each other in a manufacturing process.
(4) In an electrostatic actuator according to the present invention as stated in any one of the above items (1) to (3), a heating mechanism for heating the getter material is provided on the insulating substrate.
(5) In an electrostatic actuator according to the present invention as stated in the above item (4), the getter material is heated by supply of a heating current to the heating mechanism.
(6) In an electrostatic actuator according to the present invention as stated in the above item (4) or (5), a portion of the insulating substrate where the heating mechanism is provided is cut from a side opposite to a side where the heating mechanism is formed to thereby form a diaphragm.
(7) In an ink jet head according to the present invention, an electrostatic actuator stated in any one of the above items (1) to (6) is incorporated in the ink jet head as means for providing a driving force for discharging ink.
(8) In an ink jet head according to the present invention comprising a plurality of nozzle holes, a plurality of independent discharge chambers communicating with the nozzle holes respectively, a diaphragm formed in at least one wall of each of the discharge chambers so as to be able to be mechanically transformed, a groove provided in parallel with the diaphragm, a driving means provided in the groove for driving the diaphragm, and a common ink cavity for feeding ink to the plurality of discharge chambers, wherein when a pulse voltage is applied to the driving means, the diaphragm corresponding to the driving means is transformed in a direction so that pressure in the discharge chamber increases to discharge an ink drop toward recording paper from the nozzle hole, a getter material is disposed in the groove or in a recess portion communicating with the groove.
(9) In an ink jet apparatus according to the present invention, an ink jet head stated in the above item (7) or (8) is mounted in the ink jet recording apparatus.
(10) In a reflector type diffraction grating according to the present invention, an electrostatic actuator stated in any one of the above items (1) to (6) is incorporated into the diffraction grating as a driving means for light diffraction.
(11) In a reflector type diffraction grating according to the present invention comprising an insulating substrate having an area of a protrusion portion and an area of a recess portion, an electrode provided in the recess portion, and a thin film provided so as to cover the insulating substrate, wherein a voltage is applied between the electrode and the thin film to cause an electrostatic force to transform the thin film to be wavy by the electrostatic force generated, a getter material is disposed in the recess portion or another recess portion provided in communication with the first-mentioned recess portion.
(12) In an optical head according to the present invention, a reflector type diffraction grating stated in the above item (10) or (11) is mounted in the optical head.
(13) In a reflector type light valve according to the present invention, an electrostatic actuator stated in any one of the above items (1) to (6) is incorporated into the light valve as means for providing a driving force for the light valve.
(14) In a reflector type light valve according to the present invention comprising insulating substrates having recess portions respectively provided in two dimensions correspondingly to pixels, electrodes provided in the recess portions of the insulating substrates respectively, and thin films provided to cover the substrates respectively, wherein, when a voltage is applied between the electrode in one recess portion and corresponding one of the thin films to generate an electrostatic force, the thin film corresponding to the one recess portion is transformed by electrostatic force, getter material is disposed in each of the recess portions.
(15) In a projection type display unit according to the present invention, a reflector type light valve stated in the above item (13) or (14) is mounted in the unit.